Aqueous inkjet inks for vinyl printing require heated drying in order to remove volatile vehicle components. In most aqueous inks, the largest component is water, which is relatively easy to remove with heat due to its low boiling point (100° C.). More troublesome are glycols and other humectant solvents with high boiling points (>200° C.). While some of these components can be volatilized and removed with heat, many others cannot. Those that can be removed with heat often dry very slowly, and require high heat levels and long heating times for complete removal. Because of the slow kinetics, drying must continue long after deposition of the ink, which slows the potential throughput of the printer. High heat levels can also damage the substrate, and may create a potential hazard.
The drying process is also important because most common inkjet ink humectants have an adverse effect on the mechanical properties of the dried ink film. Scratch resistance, adhesion, and wet and dry scuff resistance can be significantly impacted by the presence of residual co-solvents. In extreme cases, the ink film never dries, and is easily wiped off the vinyl. Humectant co-solvents, however, are generally required in inkjet inks to minimize nozzle clogging that occurs when evaporation dries out the nozzles, a result known in the art as decap. Without such co-solvents, useful life of inkjet pens would be significantly shortened.